1. Field of the Invention
This invention generally relates to a liquid crystal panel drive and a method of driving a liquid crystal panel. More particularly, it relates to a liquid crystal panel drive and a method of driving a liquid crystal panel designed to improve the hysteresis of the liquid crystal panel.
2. Related Background Art
Known attempts for improving the image displaying performance of a liquid crystal panel include devices for improving the response speed of the panel as disclosed in Japanese Patent Application Laid-Open No. 3-90993 and U.S. Pat. No. 5,119,084.
These known devices are designed to improve the response speed and consequently the performance of displaying moving images of the liquid crystal panel and hence not adapted to improve the hysteresis of the panel. Therefore, there still remains the problem that the gradation of still and moving images displayed on the screen can become degraded by the hysteresis of the liquid crystal panel. Thus, there is a demand for novel methods for improving the hysteresis of a liquid crystal panel.
Like the present invention, Japanese Patent Application Laid-Open No. 7-20828 discloses an attempt for improving the hysteresis of a liquid crystal panel. The patent document proposes to prepare a table on the hysteresis of a liquid crystal panel and store it in a memory so that the performance of the liquid crystal of the panel may be corrected by referring to the table whenever necessary during the operation of the liquid crystal panel.
Japanese Patent Application Laid-Open No. 3-96993 proposes a technique for compensating the performance of the liquid crystal of a liquid crystal panel by utilizing the difference between two image signals separated by a field.
However, the techniques disclosed in the above patent documents are accompanied by the problem of structural complexity, although neither of them can achieve a satisfactorily high operating speed.
In view of the above identified existing technological problems, it is therefore the object of the present invention to provide a liquid crystal panel drive and a method of driving a liquid crystal panel designed to improve the hysteresis of the liquid crystal panel that are free from the above problems.
According to an aspect of the invention, the above object is achieved by providing a liquid crystal panel drive for driving a liquid crystal panel according to an input image signal, characterized by comprising:
a revision means for revising the reference peak level on the basis of the current level of the image signal and the current reference peak level; and
a drive signal generation means for generating a drive signal for the liquid crystal panel on the basis of the level of the signal related to the reference peak level and the level of the current input image signal;
the liquid crystal panel being driven by the drive signal.
According to another aspect of the invention, there is provided a method of driving a liquid crystal panel according to an input image signal, characterized by comprising steps of:
driving the liquid crystal panel by a drive voltage determined on the basis of the voltage brightness correction characteristic of the liquid crystal panel selected according to a signal relating to the reference peak voltage currently retained by the input image signal and the current voltage of the input image signal; and
sequentially revising the reference peak voltage on the basis of the current voltage of the input image signal and the currently retained peak voltage.